1. Field of the Invention
This invention relates to novel reactive flame retardant mixtures for use in polyurethane compositions. More particularly, this invention relates to mixtures comprising a halogenated imide-containing polyol and the corresponding ether. The polyol and ether whether combined or taken individually demonstrate flame retardant properties.
2. Description of the Prior Art
Polyurethanes are usually obtained by the reaction of polyisocyanates with polyhydroxy compounds, such as polyethers, polyesters or glycols. The problem of the flammability of these polymer compositions has received considerable attention. A variety of compounds are known that provide satisfactory flame resistance, smoke suppression and self-extinguishing properties. These conventional flame retarding agents fall within two categories. They are either reactive or additive. The reactive compounds are incorporated into the structure or backbone of the polyurethane. Additive flame retardants are only physically incorporated into the polymerized product. The additive compounds include tris(chloropropyl)phosphate and aluminum trihydrate. Both reactive and additive flame retardant compounds may be present in the same system.
Reactive flame retardant compounds offer several advantages. They provide foams with better physical properties since they are part of the compositions molecular structure and cannot be leached or washed out.
It is known to use polyol esters of tetrabromophthalic anhydride as a reactive component in the preparation of flame retardant polyurethanes.
U.S. Pat. No. 3,642,646 discloses polyol compositions useful in preparing rigid foam compositions. These polyols comprise the reaction adducts of polyfunctional aromatic carboxylic acid anhydrides or chlorendic anhydride and polyether polyols. It specifically teaches the use of half esters based on a polyol and tetrabromophthalic anhydride.
U.S. Pat. No. 3,585,185 discloses a process for preparing ester-containing polyols by the reaction of alkylene oxide condensates of organic compounds having at least two active hydrogen atoms with a halogen-containing organic acid anhydride and an alkylene oxide.
U.S. Pat. No. 3,454,530 teaches the use of polyols useful in the preparation of rigid polyurethane foams. These polyols are prepared by the reaction of a di- or tri-alkanolamine with a cyclic anhydride of an organic dicarboxylic acid and a lower alkylene oxide.
Canadian Pat. No. 993,451 discloses halogen-substituted aromatic amide-ester polyols and their use in a flame retardant flexible polyurethane foam.
U.S. Pat. No. 3,676,376 teaches the use of polyester polyols based on tetrabromophthalic anhydride, an aliphatic dicarboxylic acid, a polyol and an aliphatic diol.
U.S. Pat. No. 3,989,653 teaches the preparation of diesters of tetrabromophthalic anhydride by the reaction product of tetrabromophthalic anhydride and a polyhydroxy compound containing at least three hydroxyl groups.
U.S. Pat. Nos., 3,565,812, 3,639,541 and 3,639,542 are directed to the preparation of halogen-containing organic acid anhydrides based on ester- and phosphorous-containing polyols.
The prior art flame retardants mentioned above are esters. They are intended for use in polyurethane compositions. They have lower hydrolytic and thermal stability than the flame retardant mixture in the present invention. In addition, production of the present halogenated imide-containing polyol and ether do not require the use of an alkylene oxide such as propylene oxide. This is advantageous because alkylene oxides are toxic, explosive and require the use of pressure equipment.
Spatz et al. is "Industrial and Engineering Chemical Product Research and Development" vol. 8, no. 4, pages 397-8 (1969) teach the use of N-(2-hydroxyethyl)tetrabromophthalimide as a flame retardant in some thermoset polymeric compositions.
None of the references are directed to the halogenated imide-containing polyols and ethers of the present invention. These prior art flame retardants are limited in application to thermoset compositions or polyurethanes and are incorporated into the structure of the polymer itself.